feat(profile): add credential binding contracts

Author: loong10k

src/main/java/io/github/easy4j/hermes/security/CredentialProvider.java

@@ -0,0 +1,7 @@
+package io.github.easy4j.hermes.security;
+
+/** Resolves the current credential for a named profile on every new request. */
+@FunctionalInterface
+public interface CredentialProvider {
+    CredentialSnapshot resolve(ProfileIdentity identity);
+}